babysitting vs playgroup

babysitting

noun
  • The work of a babysitter; the care of children in the temporary absence of their parents or guardians. 

  • Hypernym: childminding 

playgroup

noun
  • An informal organised group providing care and activities for preschool children. 

  • A group of children who meet together for supervised play. 

  • A group of gamers who meet together, especially for role-playing games. 

How often have the words babysitting and playgroup occurred in a corpus of books? (source: Google Ngram Viewer )